1. Field of the Invention
The present invention relates in general to adjusting fuel and timing operations of an engine to optimize desired operating characteristics of the engine and in particular to a method and apparatus for adjusting the fuel flow and ignition timing for each engine cylinder individually to optimize desired operating characteristics of the engine as a whole.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 AND 1.98
In order to optimize engine performance with today's technology, it is well known to inject fuel into engine cylinders in a known quantity while monitoring desired engine operating characteristics such as torque, emissions, and the like. These tests are made for a plurality of engine operating RPM settings and throttle positions. Thus, for a given throttle position and engine speed, a voltage is applied to the fuel injector for a period of time known as the pulse width. The duration of the voltage pulse determines the amount of fuel injected into a cylinder. This pulse-width is varied until the optimum desired operating engine conditions that are being monitored are achieved. Then the throttle position and engine speed are changed to a new throttle position and engine speed and the desired engine operating characteristics are monitored again while the pulse-width is varied to vary the amount of fuel being injected into the cylinders and the optimum pulse-width is again noted. When this is accomplished for a desired number of throttle positions and RPM settings over a given range, the gross pulse-width data value for each throttle position versus engine RPM is stored in a two-dimensional data storage cell array. A microprocessor is coupled to the data storage cell and during engine operation, when the throttle is in a given position and the RPM is at a given setting, the microprocessor selects the pulse-width value stored in the table for that throttle position and RPM setting and causes the same desired amount of fuel to be injected into each cylinder. Thus, optimum operation of the engine as a whole is achieved based upon the desired engine operating characteristics to be achieved and, at each throttle position and RPM setting, the same pulse-width stored for that throttle position and RPM setting causes the same amount of fuel to be applied to all cylinders to cause optimum operation of the engine.
Also, for the same throttle positions and RPM settings, the timing of the ignition is varied and the desired operating characteristics of the engine are monitored until the proper ignition timing is obtained for each of the throttle positions and RPM settings to achieve the desired optimum engine operating conditions. These settings are again stored in a second two-dimensional table representing throttle position versus RPM setting. The microprocessor, again, at any given throttle position and RPM setting will look into the table and pick the ignition timing value stored therein and cause that same ignition timing to be applied to all of the cylinders to again achieve the desired optimum engine operating conditions.
It has been found, however, that a number of conditions exists which may cause a variation between the operation of one cylinder with respect to another. Thus, for instance, in a four-cycle or two-cycle engine, it has been found that the volume of the combustion chamber varies from cylinder-to-cylinder and causes variable compression rates. In addition, it has been found that there is a difference between "in-cylinder" temperatures because of a variation in cooling paths to each cylinder and the like. Further, the length of the path of the air intake and of the exhaust also varies from cylinder-to-cylinder which causes a variation in the optimum operation of one cylinder with respect to another. In addition, in two-cycle engines, exhaust tuning as well as intake and exhaust port location vary from cylinder-to-cylinder and thus create differences in operation between cylinders.
Therefore, if the same fuel control pulse width is used to cause the same amount of fuel to be applied to each cylinder and if the same ignition timing is applied to each cylinder at each given throttle position and RPM setting to cause the ignition to occur at identical crankshaft positions, the engine may not operate at its ultimate optimum operating conditions because of the variation in operation between cylinders.
Therefore, it would be advantageous if the operating characteristics of an engine could be optimized by adjusting the amount of fuel flow and ignition timing to each cylinder individually.